1. Field of the Invention
The present invention relates to a method and apparatus for dispensing a substance and, more particularly, to such a method and apparatus which are particularly well suited to the application of flowable substances as paint, lacquer, stain, and other surface treating substances.
2. Description of the Prior Art
A variety of environments exist in which the application of flowable substances is plagued by a multiplicity of problems. The problems result from such general considerations as the characteristics of the flowable substance, the surface to which the flowable substance is to be applied, the aesthetic effect desired to be achieved by the application of the flowable substance and the environment within which the application process takes place. For example, in the application of flowable substances such as paint, lacquer and the like to surfaces, these problems are particularly acute. To use a specific example for purposes of illustration, in the painting of automotive vehicles, all of these considerations interplay in such a manner as not only to require painstaking control over all aspects of the application process and long years of training to achieve an adequate result, but also render impossible the achievement of what would otherwise be the precise result desired.
Where, for example, a portion of an automotive vehicle is to be repainted, it is of course desired that the repainted surface match the existing paint. However, the conditions to which reference has previously been made cause a precise match to be unattainable. The specific reasons for this are many. The existing paint typically has deteriorated to some degree so that the original paint which was employed would not match the existing paint. Furthermore, since vehicles are typically painted at the time of manufacture by a method, such as dipping the vehicle in a paint bath, which is impractical for repainting, the differences in the methods of application inherently produce different results.
In addition to these general limitations, there are a plethora of other chronic problems with conventional methods and equipment. Conventionally, the paint is atomized during application so that by volume, in effect, a minimum amount of paint is mixed with a maximum amount of air and sprayed in the direction of the surface to be repainted. Such atomization presents a host of difficulties which are difficult, or impossible, for even the most experienced operator to control. In a given volume of the atomized paint, the paint particles are not evenly distributed so that, upon contact with the surface to be repainted, the paint is, at best, unevenly applied.
Second, because for a given volume a minimum amount of paint is present in the atomized paint, the paint is applied in very thin layers requiring numerous passes and, perhaps, more than one coat to achieve an adequate result. The process of repeatedly passing the atomized paint over the surface to be repainted inherently causes uneven application of the paint. This produces visible imperfections such as patterns, lines, thin areas, runs and the like.
Third, the atomized paint is subject to the vagaries of air currents, heat, moisture and the like causing the paint to be applied in a manner beyond the control of even the most experienced operator.
Fourth, the atomized paint is highly susceptible to contamination by the spray equipment as well as from the environment. Such contaminants as dust, grease, oil, moisture, insects and a multiplicity of other contaminants are readily attracted to and entrapped by the atomized paint resulting in a further diminishment of the result.
Fifth, the composition of the paint is difficult to control when it is atomized due to the random intermixture of the paint and air particles. This problem is particularly acute where the paint to be applied has been produced to create a particular aesthetic effect. For example, where the paint to be applied is to have a highly metallic appearance, the mica or other metallic materials within the paint are difficult, or impossible, to control where the paint is atomized. The result in the repainted surface may be such that the metallic particles are buried in the paint producing a non metallic, or flat, appearance in contrast with the existing paint.
Still further, these other chronic problems virtually ensure that the same paint cannot be applied to produce the same result by different operators, or in different environments, or even by the same operator continuously within the area being repainted.
Therefore, it has long been known that it would be desirable to have a method and apparatus for dispensing a substance which are operable to ensure that the substance can be dispensed in precisely the manner desired to achieve precisely the result desired; which are not subject to influences which cause a variation in the result achieved; which are particularly well suited to the application of such substances as paints, lacquers, and other surface treatment materials; which permit different operators in different environments to achieve the same result, thus being able to replicate the result under virtually all conditions; which permit the repainting of surfaces to achieve the same appearance as the existing paint; and which are otherwise entirely effective in achieving their operational objectives.